These appear to be fragments of black petrified wood, formed long ago, that were broken and then rounded by the waves on the coast before being deposited in a clay layer. Several pieces were collected, and clear wood grain patterns are visible. They were collected in Sankai, Aichi Prefecture, and are believed to be carbonized black petrified wood found within the Miocene sediments of the Shizaki Group. When collected, they were embedded in a clay matrix, but separated with a slight impact. In Sankai, layered claystone strata are exposed at an angle, and rounded black petrified wood is scattered throughout the cross-sections. The specific gravity was measured to be 1.7, which is lower than typical petrified wood, likely due to the remaining carbonized parts during the silica deposition process. This is indicated by the fact that it is heavier than coal but only slightly harder. I have one more, but this is the only one for sale, as it is for preservation. Approximate maximum size: 62mm x 34mm x 25mm Weight: 40g 52 1499 42 1689